The Brain

The human brain is responsible for all behaviors, thoughts, and experiences.
This module gives an introductory overview of the brain's neuroanatomy and methods to study it.

Basic Brain Structures:
- Identify and describe the functions of the brain stem, cerebellum, and cerebral hemispheres.
- Recognize and describe the four cerebral lobes: occipital, temporal, parietal, and frontal.
Split-Brain Patients:
- Describe characteristics and functions revealed through studying split-brain patients.
Gray vs. White Matter:
- Distinguish between gray and white matter of the cerebral hemispheres.
Research Methods:
- Outline common approaches to studying the human brain.
- Differentiate among neuroimaging methods including PET, fMRI, EEG, and DOI.
Resolution in Brain Studies:
- Understand spatial versus temporal resolution in the context of brain function.

Textbooks on psychology must reference the brain as it implements all described behaviors, thoughts, and experiences.
Cognitive Limitations:
- Humans cannot perform two complex tasks simultaneously (e.g., read and converse).
- Limitations might reflect shared resource consumption among behaviors (e.g., neural resources).
- Neuronal Wiring:
- Neurons have competitive wiring which can inhibit the firing of adjacent neurons, restricting responses to visual information.

The brain is generally divided into three main parts:
- Brain Stem
- Cerebellum
- Cerebral Hemispheres
Brain Stem:
- Acts as the “trunk” of the brain, responsible for vital functions like respiration, heart rate, and digestion.
- Severe damage to the brain stem results in the need for life-support systems.
- In many jurisdictions, loss of brain stem function is termed "brain dead".
- Contains the medulla, pons, midbrain, and diencephalon (thalamus and hypothalamus).
- Functions also regulate the sleep-wake cycle and other sensory and motor functions.

The cerebellum is located at the back of the brain and was historically referred to as the "small brain".
It coordinates movement and maintains posture.
Neuroimaging studies connect it to various cognitive functions including language, despite ongoing research into these roles.

Comprise the cerebral cortex and white matter along with subcortical structures (basal ganglia, amygdala, hippocampal formation).
Cerebral Cortex:
- The largest/most visible part of the brain.
- Divided into two hemispheres, with distinct gyri (folds) and sulci (grooves) giving it a gray appearance.
Lobes:
- Frontal Lobe:
- Responsible for motor planning, language, judgment, and decision-making.
- Largest lobe in humans relative to other animals.
- Parietal Lobe:
- Associated with somatosensory functions and visual attention.
- Temporal Lobe:
- Involved in vision, auditory processing, memory, and multisensory integration.
- Occipital Lobe:
- Primarily focused on vision processing.

Found beneath the cortex; include:
- Basal Ganglia:
- Involved in voluntary movement connections.
- Limbic System:
- Comprising the amygdala and hippocampal formation, central to emotion, aversion, and gratification.

Connected by the corpus callosum, cerebral hemispheres typically share sensory and motor functions with contralateral representation.
Some patients have disconnected hemispheres, revealing:
- Sensory information is processed in the hemisphere opposite its origin.
- The left hemisphere manages verbal responses, while the right may process non-verbal information.
- Implications:
- Exploring these patients demonstrates how disconnected hemispheres handle tasks independently and less competitively.

Gray Matter:
- Comprised of neuronal cell bodies and responsible for vital brain functions.
- Covered by the outer grayish layer seen in dissections and imaging.
White Matter:
- Composed of axons (neuron extensions) that transmit signals and are often myelinated.
Functional Relevance:
- Loss of gray or white matter can lead to deficits in cognitive functions like memory and reasoning.

Techniques vary and deliver evidence based on the question being explored:
Historical Methods:
- Example: Phrenology, linking skull shape to brain function.
- Although discredited, it set a foundation for localized brain functions.
Dissection:
- Critical in neuroscience for centuries; helps understand brain structure and functions through microscopic examination and staining techniques.
Neuroimaging:
- Techniques like MRI and CAT scans visualize brain structures and changes correlating with behavior.
- Lesion Studies:
- Investigating effects of induced lesions in animals or analyzing natural lesions in patients provides insights into behaviors linked to specific brain regions.

Functional Magnetic Resonance Imaging (fMRI):
- Measures changes in blood oxygen levels, reflecting neuron activity, but has poor temporal resolution.
Electroencephalography (EEG):
- Monitors electrical brain activity with high temporal resolution but poor spatial resolution.
Diffuse Optical Imaging (DOI):
- Measures changes in light absorption to infer brain activity with both high spatial and temporal resolution potential.

Ablation: Surgical removal of brain tissue.
Basal Ganglia: Subcortical structures involved in voluntary movement.
Cerebellum: Structure at the back of the brain critical for movement coordination.
Cerebral Cortex: Outermost region of the cerebrum; central to higher brain functions.
Gray Matter: Neuronal cell bodies' outer gray regions.
White Matter: Myelinated axons' inner whitish areas that conduct electrical signals.
Converging Evidence: Consistent findings from different studies enhancing the credibility of research conclusions.
Split-Brain Patient: Individual with surgically severed corpus callosum, aiding the study of hemisphere-specific functions.